A laser apparatus is a device that outputs a laser beam having three characteristics of monochromatic, coherence, and collimation, compared to natural light or light radiated from a lamp. The laser beam output from the laser apparatus have a different wavelength and a different pulse width depending on a condition in which the laser beam is generated.
Recently, technologies for treating a human body by modifying a state of a human tissue or removing a tissue by use of light has been widely used. Accordingly, there are efforts to develop therapy apparatuses utilizing various light sources, including a laser beam.
Among them, a laser therapy apparatus has different characteristics of being absorbed into a tissue depending on a wavelength of irradiated light, and polarization properties of the light may affect such characteristics. Thus, in order to select and maintain polarization properties, the laser therapy apparatus may include an optical element, such as a polarization controller and a polarization splitter.
When it comes to generating a laser beam for treatment, the laser therapy apparatus may be configured to allow the laser beam to have polarization properties indicative of dominant p-polarized light or s-polarized light, and maintain the polarization properties. However, in existing technologies, a refractive index is changed because laser alignment, internal temperature of a crystal, or strength of the laser beam is changed in the process of generating a laser beam for treatment, and the change of a reflective index frequently results in switching between the p-polarized light or s-polarized light.